Isochronal correction system

ABSTRACT

An isochronal correction system for mechanical clock movements, such as automobile clocks, enabling clockworks which have been isochronally balanced within acceptable limits to perform satisfactorily in a predetermined gravitational position, such as vertically to meet the most general or usual service mounting of the clock, nevertheless providing for utilization where for some reason, such as variation of position or accessibility of the usual clock-setting stem, the clockworks must be mounted in a different position in which it has been rotated beyond the plus or minus degrees of variation permitted by the standard, i.e., vertical, orientation accommodating the original isochronal correction. To this end, means in the form of a weight relationship on the balance wheel are provided to compensate for the deviation from the standard balancing relationship. Thereby performance characteristics substantially equivalent to the standardized isochronal correction are maintained without requiring special construction, rebalancing, or adjustment of the various parts of the clockwork assembly.

United States Patent Lawson et al.

[54] ISOCHRONAL CORRECTION SYSTEM [72] Inventors: Robert R. Lawson, Somerset;

Leonard L. Metzinger, Delavan, both of Wis.

[73] Assignee: Bunker Ramo Corporation, Oak

Brook, Ill.

[22] Filed: June 7, 1971 [21] Appl. No.: 150,586

[52] US. Cl ..58/107, 73/6 Primary Examiner-Richard B. Wilkinson As a Examine-S eele .W a1 Attorney-Frederick M. Arbuckle 1451 Oct. 3, 1972 An isochronal correction system for mechanical clock movements, such as automobile clocks, enabling clockworks which have been isochronally balanced within acceptable limits to perform satisfactorily in a predetermined gravitational position, such as vertically to meet the most general or usual service mounting of the clock, nevertheless providing for utilization where for some reason, such as variation of position or accessibility of the usual clock-setting stem, the clockworks must be mounted in a different position in which it has been rotated beyond the plus or minus degrees of variation permitted by the standard, i.e., vertical, orientation accommodating the original isochronal correction. To this end, means in the form of a weight relationship on the balance wheel are provided to compensate for the deviation from the standard balancing relationship. Thereby performance characteristics substantially equivalent to the standardized isochronal correction are maintained without requiring special construction, rebalancing, or adjustment of the various parts of the clockwork assembly.

11 Claims, 4 Drawing Figures PATENTEDmna I912 FIG.

FIG

FIG. 3-

I W2 -TU RNS I I BALANCE MOTION FIG. 2

INVENTORS ROBERT R. LAWSON LEONARDL..METZINGER This invention is concerned with an isochronal correction system for mechanical clockworks such as may be mounted in automotive vehicles.

Automobile clock movements present special 2. without departing from the spirit and scope of the novel concepts of the disclosure.

FIG. 1 is a schematic illustration of a hairspring and balance wheel mounting for a mechanical clock;

problems because they are generally subjected to hostile environments such as temperature variations, shock, vibration, varying hand loads and dirty atmosphere. The mechanism is a combination of many parts that are liable to manufacturing variations, wear and lubrication variables. As a result of these conditions, there are variations in the power that is supplied to the balance, causing balance motion changes. Part of such motion changes are cyclical and part are a gradual decrease in efficiency of the works. Therefore, it is very important to keep the isochronal error to a practical and economical minimum. The change in rate with motion is less at high balance motions, and, therefore, the clock movement is generally powered to provide high motions as it leaves the factory. It will thus be apparent that manufacturing of clocks is a continuous effort to supply aconstant delivery of power to the vibrating system that must, in turn, continue functioning with least rate variation with power changes.

Heretofore, it has been the practice to substantially cancel-out-of-poise condition in the balance assembly including the hairspring collet by incorporating the proper amount of unbalance, properly located, on the balance wheel. However, such isochronal correction must necessarily be related to some relatively fixed point of reference relative to gravity, and if the clockworks are rotated relative to such point of reference beyond a reasonable degree of tolerance, a badly unbalanced condition results. Heretofore, it has been customary, therefore, to build the clockworks having in mind the particular rotary orientation thereof in g service, and then specially building into such clockworks the desired isochronal correction. An important object of the present invention is to overcome the foregoing and other'disadvantages, defects, inefficiencies, shortcomings and problems in prior methods and structures and to attain important advantages and improvements by providing the novel isochronal correction system which will be hereinafter more particularly described.

Another object of the invention is to provide a system for isochronal correction of clockworks which will enable the works to be manufactured according to a standard isochronally corrected for one preferred gravitational orientation of the works in service and enabling selective additional isochronal correction to accommodate wide rotary variants from the predetermined gravity orientation to accommodate environmental conditions such as accessibility of the clocksetting stem, without necessitating rebuilding of any part of the clockworks.

Another object of the invention is to provide for selective isochronal correction of mechanical clockworks through simple and easily effected location of counterbalancing means on the balance wheel.

Other objects, features and advantages of the invention will be readily apparent from the following description of certain preferred embodiments thereof, taken in conjunction with the accompanying drawing, although variations and modifications may be effected FIG. 2 is a similar schematic illustration demonstrating isochronal correction according to the principles of the present invention;

FIG. 3 is a chart illustrating performance characteristics that are the basis of the isochronal correction system; and

FIG. 4 is an enlarged fragmentary sectional detail view taken substantially along the line IV-IV of FIG. 2.

In FIG. 1 is depicted a typical balance and hairspring assembly as used in a mechanical clock such as an automotive vehicle clock. A balance wheel 5 is mounted in fixed corotatable relation on an oscillating staff 7. A so-called flat helical hairspring 8 is anchored fixedly on its outer end to a stationary stud 9 fixed to a portion of the clockwork such as a frame plate 10. At its opposite or inner end, the hairspring 8 is anchored to a collet 11 which is fixed corotatively on the staff 7, the collet having been statically balanced by virtue of its shape. Static balancing of the balance wheel 5 is effected while assembled on the staff 7. After static balancing of the balance wheel 5 and the staff 7, safety roller 12 and impulse pin 13 are assembled with respectively the shaft or staff 7 and the hub portion of the balance wheel. In addition, means are provided for regulating the hairspring/balance combination after assembly into the clock movement or after any weight change is made on the balance wheel, herein comprising a movable regulator 14.

In this type of assembly, isochronal correction is generally effected by as nearly as practicable balancing two rate change characteristics, with opposite signs, to achieve a more constant rate throughout the possible range of balance motion in the timepiece. Thus, having reference to FIG. 3, a curve 15 demonstrates the rate of change with balance motion that would be caused by the hairspring if the balancewheel 5, the staff 7, roller 12 and impulse pin 13 where statically balanced as a unit. On the other hand, curve 17 shows the rate change tendency that is produced by a design unbalance of the balance wheel, here occasioned by roller 12 and impulse pin 13 which are dimensioned so that an unbalance is created in the direction and amount indicated by the vector arrow 18 (FIG. 1), that is, oriented for gravity in a normal intended vertical mounting of the clockwork. As a result of the counteraction of the two opposite isochronal errors demonstrated by the curves l5 and 17, a close-to-balanced relationship is attained deviating only slightly as indicated by the curve line 19 from a flat median 20. For practical purposes, therefore, an essentially constant net rate is attained over a wide range of balance motions, as shown. However, this substantially balanced condition prevails only when vector 18 is substantially gravity oriented in the downward direction with only relatively slight deviations permissible within an angular range that will maintain reasonable performance characteristics of the clock. In a typical example, such deviation may be within a range of plus or minus 30, that is 30 either side of the straight downward orientation of the vector 18.

In cases such as automobile clocks, a setting stem is provided. It is desirable to have standard works, but at the same time it is necessary to provide for positioning the stem at varying positions to conform to styling variations from automobile to automobile. I-Ieretofore, when it has been necessary to mount the clockwork such that there is an intolerable angular deviation from the normal gravity oriented vertical downward location of the vector 18, for the reasons such as gaining access to the time-setting stem (not shown) of the associated clock, it has been the practice to realign the balances and counterbalances in the assembly to effect proper shift of the vector 18 to the normal vertical, gravity oriented relation, or to add a gear train to effectively move the stem. Either of these solutions is a costly manufacturing procedure which substantially increases unit costs.

According to the present invention, means are provided which eliminate need for additional gear parts or structurally or relatively changing or rebalancing the parts ofthe assembly, while nevertheless attaining the desired isochronal correction resulting in the close-toflat curve performance demonstrated by the curve 19 in FIG. 3, while enabling any preferred rotary positioning or orientation for the mounting of the clockwork about a horizontal axis represented by the staff 7. In a simple and efficient attainment of this desirable result, counterbalancing weight adjustment is effected on the rim, represented as a flat band 21 of the balance wheel 5. Assuming, for example, that it is desired to'change rotary orientation of the clockworks 90, the balance wheel unbalance vector 18 must be shifted 90 from the normal vertical position into substantially the horizontal position shown in FIG. 2. An added unbalancing weight factor is added to the rim 21 on a vector 22 located on a line divergent relative to the line of the vector 18 at the opposite side of a vertical line such that the initial unbalance and the adjustment unbalance weight relationships represented by the vectors 18 and 22 will result in a vector 23, in the reoriented works of FIG. 2, equal to the original vector 18 as demonstrated in FIG. 1.

The second unbalance in the balance wheel represented by the vector 22, may be accomplished by clipping or punching material, indicated at 24, from the rim 21 diametrically opposite to the point at which the line of the vector 22 intersects the rim 21, thereby throwing the intersected area of the rim out of balance at that point.

However, the preferred manner of attaining the second unbalance to attain the vector 22 is to apply to the prescribed area of the rim 21, which is to have the second unbalance, a weight 25 of the proper value. Desirably, such a weight 25 may be a metal disk calculated at attain the desired results with the particular size and performance requirement of the balance wheel 5 and its associated operating parts. For quick and easy application of the weight 25 to the flat surface of the rim 21, a suitable adhesive or other bonding agent 27 may be applied between the facing surfaces of the weight and rim. For ease in application, the adhesive 27 may be of the pressure sensitive type commonly employed in attaching nameplates and the like to machinery. Such adhesive is readily available on the market and has excellent, durable bonding characteristics between metal surfaces and is capable of withstanding wide temperature variations as well as other atmospheric variables, shocks and vibrations, and the like.

Where the necessary rotary mounting adjustment of the associated clockwork is such that the normal vector 18 is shifted in the counterclockwise direction instead of the clockwise direction shown in FIG. 2, corresponding relocation of the unbalance identified by the vector 22 to the o opposite side of the vector line 23 from that shown in FIG. 2 will be effected. Should it be necessary to reorient the normal vector 18 180 to the upper vertical position, then in order to attain the vector 23, the second, or adjusting, unbalancing means will be directly opposite and in line with the original unbalance 13. Any other necessary deviations in the rotary placement of the assembly can be adjusted by using the same method involving proper placement of the second unbalancing weight on the rim 21 consistent with the relocation of the vector 18, in each instant to attain the adjusted unbalance vector 23.

By way of typical example, in an assembly wherein the original isochronal corrective unbalance in the balance wheel 5, provided by the roller 12 and pin 13, is on the order of 0.000621 gram acting on the radial median or center of the balance wheel rim 21 about 0.745 centimeters from the axis of rotation, and constituting vector 18, an unbalancing weight adjustment 25 of similar magnitude has been found satisfactory where the vector 18 has been shifted on the order of from the vertical gravitational orientation. To attain the proper counterbalancing effect, location of the compensatory imposed weight attained by 25 should be on the order of 0 between the vector lines 22 and 18 and the weight should be 0.000878 grams. For 180 reorientation of the normal balance wheel unbalance defined by the vector 18, it has been found desirable to about double the compensatory original unbalancing factor, namely, to about 0.001242 grams in the illustrative example placed opposite vector 18. In any weight adjusted condition of the hairspring/balance combination hairspring adjustment through the movable regulator 14 is desirably effected.

We have found that in commercial practice a tolerance of i 30 provides an acceptable position adjustment. Accordingly, the preferred system of balance adjustment provides adjustment for 60 1 30, 120 1': 30 and 180 1 30 on the following basis:

Movement Rotated Clockwise in Case Movement Rotated counterclockwise in case Weight 25 0 Code Weight 25 0 Code 0 i 30 0 0 60:30 1.000Xl8 120I 1.000X l8l20 l20i30 l.732 I8 ll 1.732X l8- l5(0) H i 30 2.000 X 18 180 III 2000 X 18 180 ITI V 9 predet rm nedstqn risntafiqns-,

precise accuracy is required, or the tolerance is reduced, the resultant 22 and weight 25 may be computed for any angular reorientation to provide resultant vector =.13.-.

From the foregoing, it will be apparent that the present invention provides a new system of isochronal correction having many advantages over prior methods. One standardized clock movement as produced by mass production assembly line techniques is adapted in a simple manner to be mounted in any required rotary relation in the clock case with assurance of uniform performance, provided the compensatory unbalance factor is provided on the balance wheel, as taught herein, where the clock movement is mounted significantly out of phase with the normal vertical gravitational isochronal correction. A significant hairspring tolerance is enabled, thus providing manufacturing economy at this point. Further economy is attained by the avoidance of any need for special gears or settings for regulating trains where a standardized orientation of the clockwork is installed but the setting stem must be located at a different-from-normal position. The only variation in manufacturing sequences from the normal assembly procedures to equip the balance wheel with the desired rotary adjustment counterbalancing resides in assembling a prealtered balance wheel where the punched in balance 24 is to be used, or

where a standard balance wheel is employed, applying the proper size weight 25 at the proper location. For either manner of attaining the novel isochronal correction, simple assembly line guiding means such as positioning fixtures, which may be coded for identification, simplify installation and enable production to proceed at continuous line speed. Similarly, in the field, replacements may be accomplished by stocking a plurality of a single universal works along with an assortment, or set, of weights 25 coded to provide any range We claim as our invention: 1. A method of isochronal correction of a hairspring/balance wheel combination for a clockwork which has been isochronally corrected for vertical gravitational orientation by providing an original unbalance but which must be mounted substantially rotated from the orientation in which the original correction was made, comprising:

effecting a compensatory imbalance on the rim of the balance wheel in a magnitude and at a point located to counterbalance the horizontal component of the original isochronal correction vector and to attain as a resultant a new gravitationally oriented unbalance vector substantially the same in magnitude as the original, but in the new downward direction, whereby isochronally corrected operation of the hairspring/balance wheel assembly is assured in the rotated mounting of the clockwork.

2. A method according to claim 1, comprising removing material from the balance wheel diametrically opposite to the point at which the compensatory unbalance is effected on the balance wheel rim.

3. A method according to claim 1, comprising applying a weight to provide the compensatory unbalance on 5. In a hairspring/balance wheel assembly for use in a clockwork and including a spiral hairspring having its outer end anchored to a stationary member and its inner end anchored to an oscillatable stafl on which is mounted corotatably a balance wheel having a rim and including means providing isochronal correction involving a vertical unbalance vector for the balance wheel in a normal vertical gravitational orientation of the assembly, but requiring mounting of the assembly with an associated clockwork rotatably out of phase with the normal gravitational orientation such that the isochronal correction is adversely altered, the improvement comprising:

unbalancing weight means on the balance wheel rim located at a point spaced angularly from said vertical unbalance vector to compensate for the rotary out-of-phase mounting and thereby restoring the isochronal correction for the assembly.

6. An assembly according to claim 5, wherein said weight means comprise a punched-out area on the balance wheel rim diametrically opposite to the point on the rim at which the weight means are located.

7. An assembly according to claim 5, wherein said weight means comprise a weight applied to the balance wheel rim.

8. An assembly according to claim 7, said weight comprising a metal disk, and means securing the disk to the balance wheel rim.

9. An assembly according to claim 8, said means securing the weight disk to the rim comprising pressure sensitive adhesive.

10. An assembly according to claim 7 wherein said rim is coded along its periphery and predetermined corresponding weights are coded for selective attachment to said rim upon a predetermined orientation of said works away from normal upright condition.

11. An assembly as set forth in claim 10 wherein said code comprises a plurality of numbered depressions in said rim and correspondingly numbered weights. 

1. A method of isochronal correction of a hairspring/balance wheel combination for a clockwork which has been isochronally corrected for vertical gravitational orientation by providing an original unbalance but must be mounted substantially rotatably out of phase relative to the normal correction, comprising: effecting a compensatory imbalance on the rim of the balance wheel at a point located to counterbalance the out-of-phase disposition of the original isochronal correction vector on a vector line angularly oriented relative to the original, but displaced, vector line to attain a new gravitational oriented vector substantially the same as the original in the downward direction, whereby isochronally corrected operation of the hairspring/balance wheel assembly is assured in the rotary outof-phase mounting of the clockwork.
 2. A method according to claim 1, comprising removing material from the balance wheel diametrically opposite to the point at which the compensatory unbalance is effected on the balance wheel rim.
 3. A method according to claim 1, comprising applying a weight to provide the compensatory unbalance on the balance wheel rim.
 4. The method of isochronally adjusting a clockwork having an oscillating balance wheel to an altered gravitational position, comprising providing an initial downward unbalance to the balance wheel in the original upright condition of the clockworks and adding an unbalance to the wheel vectorially cooperating with the original unbalance to provide a resultant vectorial unbalance in the altered position substantially the same as the initial unbalance but in the downward direction when the clockworks are in the altered position.
 5. In a hairspring/balance wheel assembly for use in a clockwork and including a spiral hairspring having its outer end anchored to a stationary member and its inner end anchored to an oscillatable staff on which is mounted corotatably a balance wheel having a rim and including means providing isochronal correction involving a vertical unbalance vector for the balance wheel in a normal vertical gravitational orientation of the assembly, but requiring mounting of the assembly with an associated clockwork rotatably out of phase with the normal gravitational orientation such that the isochronal correction is adversely altered, the improvement comprising: unbalancing weight means on the balance wheel rim located at a point spaced angularly from said vertical unbalance vector to compensate for the rotary out-of-phase mounting and thereby restoring the isochronal correction for the assembly.
 6. An assembly according to claim 5, wherein said weight means comprise a punched-out area on the balance wheel rim diametrically opposite to the point on the rim at which the weight means are located.
 7. An assembly according to claim 5, wherein said weight means comprise a weight applied to the balance wheel rim.
 8. An assembly according to claim 7, said weight comprising a metal disk, and means securing the disk to the balance wheel rim.
 9. An assembly according to claim 8, said means securing the weight disk to the rim comprising pressure sensitive adhesive.
 10. An assembly according to claim 7 wherein said rim is coded along its periphery and predetermined corresponding weights are coded for selective attachment to said rim upon a predetermined orientation of said works away from normal upright condition.
 11. An assembly as set forth in claim 10 wherein said code comprises a plurality of numbered depressions in said rim and correspondingly numbered weights. 